Invasive pest devastating popular landscaping shrub arrives in Virginia

The box tree moth caterpillar can infest and eventually kill boxwood shrubs, and it has now been detected in Virginia.

The boxwood is one of the most popular ornamental evergreen shrubs in the United States. Known for a low maintenance requirements, dense growth, and resistance to deer, these beloved ornamental plants are used in homeowners’ yards and landscaping across Virginia. Now, an invasive insect is threatening them.

According to Virginia Tech entomologist Alejandro Del-Pozo, box tree moth caterpillars are voracious insects that feed directly on the leaves of boxwoods.

“The caterpillars are known for their ability to completely strip the plant of its leaves,” Del-Pozo said. “Then, without leaves to eat, they turn to eating the bark, which can kill the plant.”

This summer, the Virginia Department of Agriculture and Consumer Services (VDACS) announced that box tree moths have been found in Virginia for the first time, specifically Clarke and Loudoun counties.

“Prior to this report, the moth had not been seen in Virginia,” Del-Pozo said. “Given that, it’s very important to spot them early and respond quickly.”

To make things worse, the caterpillars and their eggs are small, making them hard to spot among the boxwood's dense foliage. To avoid accidentally spreading them into a new area, Del-Pozo recommends that landscapers take certain precautions.

“New boxwood plants should be purchased from a certified seller that complies with the proper regulations to sell them in your county,” he said. “Refrain from moving existing boxwoods without having them certified as box tree moth-free by a relevant agency."

Saving infested shrubs is possible, but it requires early detection, Del-Pozo said. Virginia Cooperative Extension has a guide to recognizing box tree moths and the damage they cause at each stage of their life cycle.

“The sooner you can detect the presence of caterpillars, the better,” he said. “Bacillus thuringiensis — a bacterium sold as a biological pesticide — has shown some efficacy for controlling box tree moth caterpillars when applied early.”

What steps should consumers take if they think they have infested plants?

“If someone believes box tree moth is present on a plant, they should immediately contact their local Extension office and also report it to the Virginia Department of Agriculture and Consumer Services,” he said. “Fill out their Report an Invasive Species web tool, and someone from the local Extension office or VDACS will directly contact the person reporting the sighting.”

With boxwood blight – a devastating fungal disease – and now the box tree moth ravaging landscaping foliage across the state, it might seem like boxwoods are doomed in Virginia. But Del-Pozo said Virginia Tech researchers are working hard to provide science-based solutions. Faculty in the Hampton Roads Agricultural Research and Extension Center recently discovered a particular fungicide application method that seems to be effective against the blight.

“Our team has conducted field experiments addressing various aspects of this challenge,” Del-Pozo said. “We’re doing work to understand the peak activity of this insect during the year, how long it takes to go through its life stages, and the presence of naturally occurring beneficial insects associated with infested boxwoods.”

About Del-Pozo

Alejandro Del-Pozo is an assistant professor of entomology and an extension specialist at the Hampton Roads Agricultural Research and Extension Center, in Virginia Beach. His research focuses on insect ecology and improving pest control through the implementation of integrated pest management strategies in various cropping systems.

Interview

To schedule an interview, contact Margaret Ashburn in the media relations office at mkashburn@vt.edu or 540-529-0814.